In the field of telecommunication close to the terminal, radio links are increasingly gaining in importance. Cordless telephones, mobile radio terminals and the wireless “RLL” (Radio in the Local Loop) or “WLL” (Wireless Local Loop) line interfacing systems are known examples of this. An air interface known as “DECT” (Digital Enhanced (previously European) Cordless Telephone) was defined on the initiative of European companies, with the aim of specifying a standard for a universal high-performance air interface. The DECT standard is described in the documents ETS (European Telecommunication Standard) 300 175-1, . . . , 9 Oct. 1992 of the ETSI (European Telecommunication Standards Institute) and is known from these.
A DECT system allows a maximum of 120 simultaneous connections between so-called fixed parts and portable parts by which, incidentally, is meant not only mobile terminals but, as for example in the case of the wireless line interface system “Radio in the Local Loop”, also stationary system components communicating with a fixed part via air interface, which include the functionality of a portable part. In which system a maximum of 10 frequencies between 1.88 and 1.90 GHz are available and a maximum of 12 simultaneous duplex voice links (time slots, voice channels) can be implemented for each frequency.
The DECT standard also specifies interworking between DECT and “ISDN” (Integrated Services Digital Network). For this reason, time slots with a 64 kbit/s transmission rate, intended as support for ISDN, are also specified in addition to the time slots (channels) with 32 kbit/s (“Full Slots”) and 8 kbit/s (“Half Slots”) required for voice links.
Fixed parts and corresponding portable parts are generally known which support transmission rates of both 32 kbit/s “Full Slots” and 64 kbit/s “Double Slots” for the faster data transmission of, for example, 64 kbit/s or, respectively, for supporting DECT/ISDN interworking, which thus provide up to six channels with a transmission rate of 64 kbit/s; i.e., a maximum of two complete ISDN connections consisting of two “B channel” basic channels with 64 kbit/s each and one “D channel” control channel with 16 kbit/s.
These fixed parts are integrated into preexisting cordless telecommunication, RLL or WLL systems. Where there is a requirement for high transmission rates, particularly for packet data transmission, this integration is done by substituting fixed parts which support both 32 kbit/s time slots (full slots) and 64 kbit/s time slots (double slots) for the fixed parts which only provide time slots of 32 kbit/s. A problem arising with this procedure is the fact that fully functional fixed parts are removed from existing networks or radiotelecommunication systems even though their procurement costs have not yet been amortized in some cases.
After the substitution, the availability of full-slot connections and double-slot connections is guaranteed, in principle. However, if there is a large number of existing full-slot connections, the case may occur that requested double-slot connections cannot be implemented since, due to the existing full-slot connections, it is not possible to form time slots with 64 kbit/s transmission rate (double slot). In this case, channels for services having a requirement for high transmission rates, especially the transmission of packet data, can only be provided again when the number of existing full-slot connections has been reduced.
From U.S. Pat. No. 4,748,681, a telecommunication system is known in which a fixed part is, in each case, operated in a radio cell. The radio cells in each case exhibit a multiplicity of different portable parts which need different services and the fixed part at least partially supports these different services and informs the portable parts via signaling of the services supported.
The present invention is directed toward specifying a method for controlling the distribution of transmission rates in a cellular radiotelecommunication system in which the radio transmission resources available in the radiotelecommunication system, especially with an RLL or WLL system, respectively, are effectively used.